What is sensorineural hearing loss?

Sudden sensorineural hearing loss (SSHL) is also known as sudden deafness. It occurs when you lose your hearing very quickly, typically only in one ear. It can happen instantly or over a span of several days. During this time, sound gradually becomes muffled or faint.

Frequencies measure sound waves. Decibels measure the intensity, or loudness, of the sounds we hear. Zero is the lowest decibel level, which is close to complete silence. A whisper is 30 decibels, and normal speech is 60 decibels. A loss of 30 decibels in three connected frequencies is considered SSHL. This means that a hearing loss of 30 decibels would make normal speech sound like a whisper.

There are about 4,000 cases of SSHL diagnosed every year in the United States. The condition most commonly affects people between ages 30 and 60. About 50 percent of people with unilateral SSHL (only one ear is affected) recover within two weeks if they get prompt treatment. About 15 percent of people with the condition have hearing loss that gradually gets worse over time. But, advances in technology used for hearing aids and cochlear implants are helping to improve communication for people affected by hearing loss.

SSHL is a serious medical condition and requires prompt medical attention. Call your doctor right away if you think you’re experiencing SSHL. Early treatment can save your hearing.

Learn more: Hearing loss on one side »

SSHL happens when the inner ear, the cochlea in the inner ear, or the nerve pathways between the ear and the brain become damaged.

Most of the time doctors don’t find a specific cause for unilateral SSHL. But, there are more than 100 causes of bilateral (both ears) SSHL. Some of the possible causes include:

  • malformation of the inner ear
  • head injury or trauma
  • prolonged exposure to loud noise
  • neurologic conditions, such as multiple sclerosis
  • an immune system disease, such as Cogan syndrome
  • Meniere disease, which is a disorder that affects the inner ear
  • Lyme disease, which is an infectious disease that’s often transmitted through tick bites
  • ototoxic medication, which can harm the ear
  • venom from a snake bite
  • blood circulation problems
  • abnormal tissue growth or tumors
  • blood vessel disease
  • aging

Congenital SSHL

Babies can be born with SSHL. This may happen as a result of:

  • infections that pass from the mother to the child, such as rubella, syphilis, or herpes
  • Toxoplasma gondii, which isa parasite that passes through the womb
  • genetic, or inherited, factors
  • low birth weight

Approximately nine out of 10 people with SSHL experience hearing loss in only one ear. You may notice hearing loss right after you wake up in the morning. You may also become aware of it when you use headphones or hold a phone to your affected ear. Sudden hearing loss is sometimes preceded by a loud popping sound. Other symptoms include:

  • trouble following group conversations
  • muffled conversation sounds
  • inability to hear well when there’s a lot of background noise
  • difficulty hearing high-pitched sounds
  • dizziness
  • balance problems
  • tinnitus, which occurs when you hear ringing or buzzing sounds in your ear

When to test your child’s hearing

Hearing loss can develop in children as a result of infections at birth or damage caused by ototoxic medications. It may not always be easy to know if your child is hearing correctly. You should have your child’s hearing tested if they:

  • don’t seem to understand language
  • don’t attempt to form words
  • don’t appear to startle at sudden noises or respond to sounds in a way you would expect
  • have had numerous ear infections or problems with balance

To diagnose SSHL, your doctor will ask you about your medical history and perform a physical exam. Make sure to tell your doctor about other medical conditions you may have and about any over-the-counter and prescription medications you’re taking.

During the physical exam, your doctor may ask you to cover one ear at a time while listening to sounds at different volumes. Your doctor may also perform some tests using a tuning fork, which is an instrument that can measure vibrations in the ear. Your doctor uses the results of these tests to check for damage to the parts of the middle ear and eardrum that vibrate.

Audiometry tests can check your hearing more thoroughly and precisely. During these tests, an audiologist will test your hearing ability using earphones. A series of different sounds and volume levels may be sent to each ear individually. This can help determine the level at which your hearing begins to fade.

An MRI scan may also be ordered to look for any abnormalities in your ear, such as tumors or cysts. MRI takes detailed pictures of your brain and inner ear, which can help your doctor find the underlying cause of SSHL.

Early treatment may increase your chances for a full recovery. But, your doctor will try to find the cause of your hearing loss before starting treatment.

Steroids are the most common treatment. They can reduce inflammation and swelling. This is especially helpful in people who have diseases of the immune system, such as Cogan syndrome. Your doctor may also prescribe antibiotics if an infection is the cause of your SSHL.

In some cases, a doctor can surgically insert a cochlear implant into your ear. The implant doesn’t completely restore hearing, but it can amplify sounds to a more normal level.

Learn more: Gene therapy makes cochlear implants more effective »

About two-thirds of people with SSHL will experience partial recovery of their hearing. One study found that 54.5 percent of people with SSHL showed at least partial recovery in the first 10 days of treatment. The recovery is more complete among individuals who experience either high- or low-frequency hearing loss, compared with those whose hearing loss is across all frequencies. Only about 3.6 percent of people with SSHL will fully recover their hearing. There is less chance of recovery among older adults and those with vertigo.

Hearing aids and telephone amplifiers can help if your hearing doesn’t improve. Sign language and lip reading can also improve communication for people with severe hearing loss.